Pharmaceutical preparations which provide a peroral dosage form of mirtazapine are known in the form of tablets having strengths of the medicinally active ingredient of from 15 to 45 mg mirtazapine.
Although the known tablets are generally acceptable as far as their medicinal activity is concerned, the solid dosage form imposes restrictions on the pharmaceutical use of mirtazapine. Some patient populations have a difficulty, physical or psychological, in swallowing solid dosage forms. If a liquid dosage form were available, these patients could more easily take the required dose of mirtazapine, having it administered in the form of an oral liquid preparation.
In general, stabilised solutions of several antidepressants, including mirtazapine, in admixture with water and methionine, and not restricted to any particular concentration of mirtazapine, are known from EP 431 663. Although these solutions are stable and are suitable, in principle, for both parenteral and oral administration, a further improvement in the specific case of peroral administration of mirtazapine is desired. For, in the case of mirtazapine, a specific problem resides in that a local anaesthetic effect is experienced upon peroral administration of a solution within the general disclosure of EP 431 663, specifically having a concentration of mirtazapine of higher than 5 mg/ml. It is an object of the present invention to overcome this problem.